I used the shareware Paintshop 3, then got into PaintShop Pro 1, 3, 5, 7, 9, 11, X4. I had a pattern going until the last. PSP 7 is the best balance of ease of control and actually being able to paint with pixels, IMO.
Photoshop Elements 10 is faster, but I like PSP's controls better. Can't seem to stray too far.
open air testing rig in basement:
Core i7 4790k 4.5GHz Vcore 1.21v, HT enabled; Gigabyte GA-Z97X Gaming 7, f6
2x4GB Crucial Ballistix UltraLow Profile DDR3-1600 9-9-9-24@1600MHz Vdimm 1.35v
Intel 4600 graphics using 1GB system memory; Samsung 840 EVO 500GB SSD
various heatsinks (depends on what I am testing ATM); Seasonic X-460FL (fanless)